1. Field of the Invention
The present invention generally relates to a mounting portion of a water jet pump of a personal watercraft, and a personal watercraft. More particularly, the present invention relates to a mounting portion including a pump casing and a pump bracket configured to fasten the pump casing to a body of a personal watercraft, and a personal watercraft comprising the mounting portion.
2. Description of the Related Art
In recent years, water-jet propulsion personal watercraft have been widely used in leisure, sport, rescue activities, and the like. A typical personal watercraft comprises a body including a hull and a deck covering the hull from above, and is equipped with an engine in a space inside the body. A water jet pump is equipped in a pump room formed on a rear bottom portion of the body. The water jet pump is configured to be driven to propel the watercraft. Specifically, a water intake is provided at a rearward position of a hull bottom surface, and a water intake passage extends rearward from the water intake to the water jet pump equipped in the pump room. Furthermore, a rear portion of the water passage is coupled to a pump bracket fastened to a front wall of the pump room. A pump casing that accommodates an impeller is mounted to the pump bracket from rearward, and a pump nozzle is connected to the rear portion of the pump casing.
A propeller shaft is coupled to a crankshaft of the engine. The propeller shaft extends rearward and is coupled to a pump shaft disposed within the pump casing. The impeller is attached on the pump shaft. When the engine operates, the impeller within the pump casing rotates integrally with the crankshaft. Water is sucked though the water intake from outside. The water is pressurized and accelerated by the rotation of the impeller, and is ejected rearward from the pump nozzle. As a result, the personal watercraft is propelled.
There are a variety of mounting portions including the pump casing and the pump bracket configured to fasten the pump casing to the body of the watercraft. One exemplary mounting portion is disclosed in Japanese Laid-Open Patent Application Publication No. 2002-308183, in which a diagonal-flow type pump casing with an inner diameter that increases rearward is mounted to a pump bracket. In this mounting portion, a seal element for exclusive use is provided between the pump casing and the pump bracket. The seal element serves to inhibit reduction of pumping efficiency, which may be caused by air flowing from the pump room side of the hull into the pump casing. The seal element is made of flexible rubber having a relatively large thickness. The seal element is provided to cover substantially the entire of an outer peripheral surface and a front end surface of a front end portion of the substantially tubular pump casing. The pump casing is mounted to the pump bracket in a sealed condition, regardless of some displacement between the pump casing and the pump bracket in a mounting operation, in such a manner that the pump casing with the seal element is inserted into the pump bracket from rearward.
However, in the mounting portion disclosed in the above Patent Publication No. 2002-308183, it is necessary to manufacture a seal element for exclusive use having a unique shape according to outer dimensions of the pump casing and the pump bracket. Furthermore, since a contact area between the seal element provided to cover the pump casing and the pump bracket is large, the seal element may be displaced or deformed by contact with the pump bracket in the mounting operation.